1. Field of the Invention
This invention relates to a contact lens for intraocular observation which is employed in diagnosis or medical treatment of an eyeball and is capable of optically recognizing an inner portion of an eyeball such as an anterior chamber angle portion, an eyeground portion and the like.
In diagnosis or medical treatment of an eye in ophthalmology, there is a case wherein observation of an inner portion of an eyeball is necessitated. For instance, with respect to the anterior chamber angle portion situated on the periphery of an anterior chamber of the eyeball, an abnormality such as in width, in opening degree or in adhesion thereof, relates to a degree of intraocular pressure, generation of glaucoma or the like. With respect to the disc optic situated on the eyeground of the eyeball, an abnormality in a size thereof or the like relates to generation of the various illnesses or the like. Accordingly, the diagnosis of an eye is carried out by observing the anterior chamber angle portion or the disc optic.
Furthermore, it is difficult to directly perform the observation of the inner portion of the eyeball. Therefore, generally, a so-called contact lens for intraocular observation which can optically recognize the inner portion of the eyeball by contacting the contact lens on the surface of a cornea of an eye to be inspected through a light ray transmitted through the inner portion of the contact lens, has been in use. As for the contact lens for intraocular observation, various constructions thereof such as a beam-transmitting type, a beam-reflecting type or the like have conventionally been proposed, as shown in Japanese Examined Patent Publication No. 13039/1974, which is selectively employed in accordance with a portion to be observed.
Concerning the diagnosis of an eye or the like, there is a case wherein an angle of opening of the anterior chamber angle portion or dimensions of the disc optic or the like should specifically be measured, as stated above, as well as optically recognizing the inner portion of an eyeball.
In that case, to obtain high measurement accuracy, it is necessary to perform direct measurement of an image of the inner portion of an eyeball which is observed through the contact lens for intraocular observation, by optically recognizing the image by superposing a pertinent index such as a protractor, a scale or the like, on the image of the inner portion of an eyeball.
It can be suggested that for instance, a pertinent index is provided on an optical path between the contact lens and an observer (ophthalmologist or the like), at outside the contact lens for intraocular observation, such that the image of the inner portion of an eyeball which is observed through the contact lens, and such an index can be optically recognized by superposing them.
However, the observation employing the contact lens is normally carried out by employing a microscope or the like. Therefore, the index should be provided inside of the microscope or the like, which is difficult to install.
Moreover, even when the index can be provided inside of the microscope, since the index should be changed for measuring an angle, for measuring a distance or the like, in accordance with the portion to be observed in an eye, the changing operation is troublesome.
Furthermore, in employing the index for measuring a distance, since the portion to be observed is magnified by the microscope, the scale of the index should be converted at every time when the magnification of the microscope is changed. This operation is troublesome which hampers smooth observation or diagnosis.